Method of x-ray diffraction topography of monocrystals and apparatus for effecting same

ABSTRACT

A method of X-ray diffraction topography of monocrystals, consisting in irradiation of every point of an investigated area of the cross-section of a monocrystal by X-rays and separation of the radiation diffracted at a specific angle from said every point of the investigated area of the cross-section of the monocrystal, simultaneously for all these points of the investigated area. An apparatus for X-ray diffraction topography of monocrystals, realizing the above method, comprising a source of X-rays and an investigated monocrystal, a collimator, a radiation detector and a means for recording the topogram of the monocrystal, positioned successively in the path of the Xradiation. The collimator, of which the direction of collimation is oriented at a specified orientation angle in relation to the crystallographic axes of the monocrystal, is in the form of a two-dimensional matrix of parallel capillaries.

United States Patent 1 Efanov et al.

[ Sept. 3, 1974 METHOD OF X-RAY DlFFRACTlON TOPOGRAPHY OF MONOCRYSTALSAND APPARATUS FOR EFFECTING SAME [76] Inventors: Valery PavlovichEfanov, ulitsa Profsojuznaya, 96, kv. 192, Moscow; Nikolai lvanovichKomyak, Kostromskoi prospekt, 22, kv. 71, Leningrad; VsevolodGrigorievich Ljuttsau, ulitsa Garibaldi, 19, korpus l, kv. 49, Moscow;Nikolai Vasilievich Rabodzei, ulitsa Institutskaya, 6a, kv. 39, FryazinoMoskovskaya oblasti, all of USSR.

[22] Filed: Jan. 24, 1973 [21] Appl. No.: 326,335

[30] Foreign Application Priority Data Jan. 28, 1972 U.S.S.R 1743310Jan. 28, 1972 U.S.S.R .1 1747007 [52] US. Cl. 250/273, 250/274 [51] Int.Cl. G0ln 23/20 [58] Field of Search 250/272, 273, 274, 275, 250/276 [56]References Cited UNITED STATES PATENTS 2,549,987 4/1951 Parrish 250/272Primary ExaminerJames W. Lawrence Assistant Examiner-C. E. ChurchAttorney, Agent, or Firm-Holman & Stern [5 7 ABSTRACT A method of X-raydiffraction topography of monocrystals, consisting in irradiation ofevery point of an investigated area of the cross-section of amonocrystal by X-rays and separation of the radiation diffracted at aspecific angle from said every point of the investigated area of thecross-section of the monocrystal, simultaneously for all these points ofthe investigated area. An apparatus for X-ray diffraction topography ofmonocrystals, realizing the above method, comprising a source of X-raysand an investigated monocrystal, a collimator, a radiation detector anda means for recording the topogram of the monocrystal, positionedsuccessively in the path of the X-radiation. The collimator, of whichthe direction of collimation is oriented at a specified orientationangle in relation to the crystallographic axes of the monocrystal, is inthe form of a two-dimensional matrix of parallel capillaries.

3 Claims, 2 Drawing Figures PATENTED 3 974 SHEET 10F 2 PATENTEU SEP 3 74SHEET 20F 2 METHOD OF X-RAY DIFFRACTION TOPOGRAPHY OF MONOCRYSTALS ANDAPPARATUS FOR EFFECTING SAME BACKGROUND OF THE INVENTION The inventionrelates generally to methods of detection of flaws in the crystallinestructure of solids and to apparatus for effecting same, and moreparticularly, it relates to methods of X-ray diffraction topography ofmonocrystals and to apparatus for effecting same.

There are known methods of X-ray diffraction topography of monocrystals,wherein all the points of an investigated area of the cross-section of amonocrystal are irradiated by X-rays, whereafter the radiationdiffracted at a specified angle from all the points of the investigatedarea of the cross-section of the monocrystal is separated, and thetopogram of the monocrystal is obtained.

In these known methods, the recording of the topographic images of allthe points of the investigated area of the crosssection of a monocrystalis effected either by obtaining the complete diffraction image of agiven point (e.g., with the use of a photographic film), separating onlythe diffracted radiation corresponding to a specified angle (or todeflection from the angle), or else by setting the receiving slot (e.g., that of a scintillation detector) directly to a positioncorresponding to this specified angle and by transmitting the electricsignal produced by this detector to a recording device to register theinformation representing the state of the monocrystal at this givenpoint of the cross-section thereof.

When passing from one given point to another, there is shifted eitherthe photographic film, to produce the complete diffraction image of thisother point, or else the cording device, so that the latter willregister in this new position the information representative of theflaws of the crystalline structure of the monocrystal in this otherpoint.

Apparatus for X-ray diffraction topography of monocrystals, are alsoknown in the art realizing the above known methods.

In these known apparatus, the radiation from a source of X-rays isdiffracted on a monocrystal being investigated, whereafter thisdiffracted radiation is made to pass through a collimator of which thedirection of collimation is oriented at a specified orientation angle inrelation to the crystallographic axes or the reticular planes of thismonocrystal and to fall on a radiation detector and a device forrecording the topogram of the monocrystal.

In these known apparatus, the source of X-rays is in the form of anX-ray tube producing either a narrow beam of X-rays, or else a beamwhich is subsequently collimated, while the collimator, oriented at aspecified angle in relation to the crystallographic axes of theinvestigated monocrystal, is in the form of a single channel which, moreoften than not, is the receiving slot of the detector, oriented at aspecified angle in relation to the axes of the monocrystal.

When these known apparatus are operated, the investigated monocrystaland the recording device are synchronoulsy displaced relative to theX-ray beam that is fixed in space, whereby the recording deviceregisters unambiguously the intensity of the radiation transduced by thedetector, as a function of the position of the monocrystal in respect ofthe beam of X- rays falling thereupon.

A disadvantage of the above described known apparatus realizing theknown methods is the necessity of ensuring high-precision adjustment ofthe system, as well as high-precision mechanical displacement of themonocrystal, accurately synchronized with the accompanying displacementof the recording means.

Among the short comings of the complicated process of topographyeffected by these known appartus realizing the known methods are therelatively slow rate of the investigation as well as the impossibilityof subjecting the investigated monocrystal to any additional actiondirectly in the process of topography.

SUMMARY OF THE INVENTION It is an object of the present invention todevelop a method of X-ray diffraction topography of monocrystals, whichwill provide for speeding up the process of obtaining topograms ofmonocrystals.

Another object of the present invention is to develop a method of X-raydiffraction topography of monocrystals, which will also provide forinvestigating the dynamics of origination and development of flaws inthe crystalline structure of monocrystals.

Still another object of the present invention is to provide an apparatusfor X-ray diffraction topography of monocrystals, realizing the abovemethod.

A further object of the present invention is to provide an apparatus forX-ray diffraction topography of monocrystals, which will provide forelimination of any mechanical displacement of the units of the apparatusin the process of topography.

These and other objects are attained in a method of X-ray diffractiontopography of monocrystals, consisting in irradiation of every point ofan investigated area of the cross-section of a monocrsystal by X-rays,separation of the radiation diffracted at a specified angle from everysaid point of the investigated area of the cross-section of themonocrystal and obtaining the topogram of the monocrystal, in whichmethod, in accordance with the present invention, the separation of theradiation diffracted at a specified angle from every the point of theinvestigated area of the cross-section of the monocrystal is effectedsimultaneously for every the point of the investigated area.

In an apparatus for realizing the herein disclosed method of X-raydiffraction topography of monocrystals, wherein the radiation from asource of X-rays is diffracted on a monocrystal, whereafter thediffracted radiation is made to pass through the main collimator ofwhich the direction of collimation is oriented at a specified angle inrelation to the crystallographic axes of the monocrystal and to fallupon thhe radiation detector to be registered by a recording means, inaccordance with the present invention, the main collimator includes atwo-dimensional matrix of parallel capillarres.

It is advisable that the apparatus include an auxiliary collimatorpositioned upstream of the monocrystal in the direction of theX-radiation, the direction of collimation of the auxiliary collimatorbeing oriented at an angle in relation to the crystallographic axes ofthe monocrystal, which is equal to the angle of orientation of the maincollimator, so that the X-radiation that has passed through theauxiliary collimator will also pass,

after having been diffracted on the monocrystal, through the maincollimator.

Due to such an embodiment of the herein disclosed apparatus for X-raydiffraction topography of monocrystals, realizing the herein disclosedmethod, the distance between the source of X-rays and the radiationdetector can be reduced to 2.0 mm to 10.0 mm, which results in asubstantial reduction of the time of obtaining a topogram.

Furthermore, the herein disclosed apparatus realizing the hereindisclosed method, due to the separation of the radiation diffracted at aspecified angle from every point of the investigated area of thecross-section of the monocrystal simultaneously for all the points, aswell as to the reduced time of topography, makes it possible toinvestigate the dynamics of origination and development of various flawsin the crystalline structure of monocrystals, directly in the process ofmanu facture of various semiconductor devices (p-n junctions, integralcircuits incorporating monocrystals).

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be furtherdescribed in connection with an embodiment thereof, with referece beinghad to the appended drawings, wherein:

FIG. 1 is a schematic view of an apparatus for X-ray diffractiontopography of monocrystals, realizing the herein disclosed method; and

FIG. 2 is an enlarged perspective view of portion A of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now inparticular to the appended drawings, the apparatus for realizing themethod of diffraction topography of monocrystals in accordance with thepresent invention, comprises a source 1 (FIG. 1) of X-rays and thefollowing units positioned along the path of the radiation coming fromthis source 1: a collimator 2, an investigated monocrystal 3 (silicon)in the form of a flat-parallel plate possessing pre-establishedcrystallographic characteristics (syngony, lattice spacing, orientationof the crystallographic or reticular planes in relation to the faceplanes), at collimator 4, a detector 5 and a means 6 for recording thetopogram of the monocrystal 3.

The collimator 4 is the main collimator of which the direction ofcollimation is oriented at a specified orientation angle (which is theBragg angle 6) in relation to the crystallographic axes of themonocrystal 3. The. collimator 4 is in the form of a two-dimensionalmatrix made up by a system of parallel capillary tubes 7 (FIG. 2), thediameter of these capillary tubes being approximately microns.

However, in an apparatus embodying the present invention, the maincollimator may be in the form of a two-dimensional matrix made up by asystem of parallel capillaries of any suitable shape and size.

The collimator 2 is the auxiliary collimator which has a structuresimilar to that of the main collimator 4, i.e, it is a two-dimensionalmatrix including a system of parallel capillaries 8, the direction ofcollimation of this auxiliary collimator 2 being oriented at anorientation angle in relation to the crystallographic planes of themonocrystal 3, which is equal to the orientation angle of the maincollimator 4, whereby the X-radiation that has passed through thisauxiliary collimator 2 is made to pass, after having been diffracted onthe monocrystal 3, through the main collimator 4.

However, the structure of the auxiliary collimator may be different fromthat of the main collimator, as far as both the shape and thearrangement of the capillaries of the matrix are concerned.

It is possible to embody an apparatus realizing the method according tothe present invention, having only the main collimator. However, in thisembodiment, the contrast of the topogram on the detector is not as good.

The source 1 of X-rays in the presently described embodiment is in theform of a high-voltage cathode ray tube incorporating a target anode 9which is a coating on the beryllium outlet window 10, a cathode l1 and adeflection system 12, electrically connected to a power unit 13including a scanning control system.

The detector 5 in the presently described embodiment is in the form of atarget of an X-ray responsive television-type transmitting tube 14incorporating a cathode l5 and a deflection system 16, electricallyconnected to a power unit 17 including a scanning control system.

The means 6 for recording the topogram of the monocrystal 3 is in theform of a television-type receiving cathode ray tube electricallyconnected to the transmitting tube 14.

However, an apparatus realizing the herein disclosed method of X-raydiffraction topography of monocrystals may employ any other known kindof radiation detector (photographic film included) capable of anunambiguous registration of the position of a point on a plane and ofthe intensity of the radiation corresponding to this point. If aphotographic film is employed as the radiation detector, it would thenserve both as the detector and the means for recording the topogram of amonocrystal.

The herein disclosed apparatus further incorporates a means (not shown)for fixing in place the source 1 of X-rays, the monocrystal 3, thecollimators 2 and 4 and the detector 5, proving for the adjustment ofthe respective positions of the above-listed components and ensuringrigid fixation thereof in the course of production of a topogram.

The operation of the herein disclosed apparatus for X-ray diffractiontopography of monocrystals, realizing the method in accordance with theinvention, is as follows.

When a negative potential of 10 to 40 kV is applied to the cathode 11(FIG. 1) of the cathode ray tube 1 (the target anode 9 of the tube beinggrounded), there is produced, across the target anode 9, an X-radiation18 which issues in the form of a wide cone.

The collimator 2 selects from this cone 18 of X-rays only that direction19 of radiation which is directed at the Bragg angle 0 in relation tothe selected system of the reticular planes of the monocrystal 3 beinginvestigated.

However, if the auxiliary collimator is omitted from the structure ofthe apparatus, the monocrystal itself would select the requireddirection from the cone of the X-rays, but then the signal-to-noiseratio at the detector would not be as good.

As a result of the diffraction of the X-rays on the investigated area ofthe cross-section of the monocrystal 3, there emerges from the lattermonochromatic radiation originated by the material of the target anode 9as a beam 20 of parallel rays, oriented in a direction depending on theBragg angle 6 for the given type of the monocrystal 3 as a whole andalso weakened dissipated radiation (not shown). The radiation passesthrough the capillaries 7 of the collimator 4, whereby the radiationdiffracted at a specified angel (the Bragg angle is separated in theform of the above-mentioned beam 20 of parallel X-rays from every pointof the investigated area of the cross-section of the monocrystal 3,simultaneously for every point of this investigated area. This beam 20of parallel X-rays falls upon the detector in the form of an image ofthe topogram of the crosssectional structure of the investigated area ofthe monocrystal 3. The detector 5 transmits this image of the topogramto the recording device 6, i.e. to the television-type receiving tube.

The dissipated radiation and the radiation diffracted at other angles issubstantially weakened by the material of the collimator 4.

If, in the course of initial positioning of the components, the anglebetween the selected system of the crystallographic (reticular) planesof the the monocrystal 3 and the direction of collimation of thecollimator 4 is not equal to the Bragg angle, the monocrystal 3 iscoarsely angularly adjusted, until an image appears on the screen of thereceiving television-type tube, in which position the monocrystal 3 isretained. The same result can be obtained by rotation of the collimator4. Thereafter the collimator 2 is introduced to step up the contrast ofthe image.

If a series of monocrystals of a single type is to be investigated, thecollimators 2 and 4 are so selected, that the angle between the faceplanes of the monocrystal 3 and the direction of collimation of thecollimators 2 and 4 are equal to the Bragg angle for this type ofmonocrystals. In this case, the relative positioning of the collimators2 and 4 is adjusted but once and retained throughout the entire seriesof investigations. In this way, relative positioning and adjustment ofthe collimators 2 and 4 and the monocrystal 3 is substantiallysimplified. When monocrystals of a different type are to beinvestigated, the whole collimator assembly is replaced.

While the primary electron beam approximately microns in diameter scansthe target anode 5, a corresponding beam of X-rays successivelytraverses the investigated monocrystal 3. In each point of theinvestigated area, provided that the Bragg condition for the monocrystalas a whole is observed therein, there takes place diffraction of theincident beam, and the diffracted beam, after having passed through thecollimator 4, is received by the detector 5.

Irradiation by X-rays of the entire cross-sectional area of themonocrystal may be effected simultaneously as well, and this would notconstitute any departure from the scope of the present invention, butinvolve the incorporation of a source of X-rays which is at presentunprofitable from the point of view of its specific power output; on theother hand, the incorporation of the source of X-rays with a scanningbeam is preferable becuase with the same power consumption its capacityis greater by 3 to 4 orders of magnitude.

All the components of the herein disclosed apparatus being rigidly fixedthroughout the process of obtaining a topogram of the monocrystal 3,there is offered a principally new possibility of repeating a series ofinvestigations of the same rigidly fixed monocrystal 3 subjected tovarious kinds of external action, e.g., mechanical, thermal, etc.

The herein disclosed apparatus realizing the method in accordance withthe present invention may be successfully employed for control of thequality of monocrystals, as part of production of various semiconductorand laser devices. Due to speedy obtainment of a topogram and to thesimplisity in operation and maintenace, the herein disclosed apparatusmay be employed, for instance, for mass control of monocrystals in themanufacture of integral circuits.

Furthermore, the apparatus realizing the herein disclosed method may beemployed in scientific research, since it enables the investigation ofthe dynamics of the development of various flaws in the crystallinestructure of monocrystals in the course of their growth, as well asthose resulting from an external action.

What is claimed is:

1. A method of X-ray diffraction topography of monocrystals, comprisingthe steps of: irradiating every point of an investigated area of thecross-section of a monocrystal by X-rays; separating the radiationdiffracted at a specified angle from every point of the investigatedarea of the cross-section of the monocrystal simultaneously for all thepoints of the investigated area from the radiation diffracted at allother angles; and providing a topogram of the monocrystal.

2. An apparatus for X-ray diffraction topography of monocrystals, saidapparatus comprising: a source of x-rays; an investigated monocrystalpositioned behind said source of X-rays in the path of the radiationissuing therefrom so that said radiation is diffracted by saidmonocrystal; a main collimator positioned behind said investigatedmonocrystal in the path of said defracted X-radiation being formed as atwo-dimensional matrix of parallel capillaries the direction ofcollimation of said main collimator being oriented at a given angle tothe crystallographic axes of said investigated monocrystal and throughwhich the radiation diffracted at the given angle to thecrystallographic axes of said investigated monocrystal passes from eachpoint of the cross-section of said investigated monocrystal with theexclusion of radiation diffracted at all other angles; a detectorpositioned behind said main collimator in the path of said diffractedX-radiation so that said diffracted X-radiation falls on said detector;and means for recording topogram of said monocrystal, said recordingmeans positioned behind said detector in the path of said diffractedX-radiation.

3. An apparatus as claimed in claim 2, further comprising an auxiliarycollimator positioned in front of said investigated monocrystal in thepath of said X- radiation, the direction of collimation of saidauxiliary collimator being oriented at an orientation angle in relationto said crystallographic axes of said investigated monocrystal which isequal to said orientation angle of said main collimator so that saidX-radiation passing through said auxiliary collimator is made to pass,after having been diffracted on said monocrystal, through said maincollimator.

1. A method of X-ray diffraction topography of monocrystals, comprisingthe steps of: irradiating every point of an investigated area of thecross-section of a monocrystal by Xrays; separating the radiationdiffracted at a specified angle from every point of the investigatedarea of the cross-section of the monocrystal simultaneously for all thepoints of the investigated area from the radiation diffracted at allother angles; and providing a topogram of the monocrystal.
 2. Anapparatus for X-ray diffraction topography of monocrystals, saidapparatus comprising: a source of x-rays; an investigated monocrystalpositioned behind said source of X-rays in the path of the radiaTionissuing therefrom - so that said radiation is diffracted by saidmonocrystal; a main collimator positioned behind said investigatedmonocrystal in the path of said defracted X-radiation being formed as atwo-dimensional matrix of parallel capillaries the direction ofcollimation of said main collimator being oriented at a given angle tothe crystallographic axes of said investigated monocrystal and throughwhich the radiation diffracted at the given angle to thecrystallographic axes of said investigated monocrystal passes from eachpoint of the cross-section of said investigated monocrystal with theexclusion of radiation diffracted at all other angles; a detectorpositioned behind said main collimator in the path of said diffractedX-radiation so that said diffracted X-radiation falls on said detector;and means for recording topogram of said monocrystal, said recordingmeans positioned behind said detector in the path of said diffractedX-radiation.
 3. An apparatus as claimed in claim 2, further comprisingan auxiliary collimator positioned in front of said investigatedmonocrystal in the path of said X-radiation, the direction ofcollimation of said auxiliary collimator being oriented at anorientation angle in relation to said crystallographic axes of saidinvestigated monocrystal which is equal to said orientation angle ofsaid main collimator so that said X-radiation passing through saidauxiliary collimator is made to pass, after having been diffracted onsaid monocrystal, through said main collimator.